mose problems PLZ HELP

Heres the problem. I have this problem for a while where my mouse would change speeds on it's own. Sometimes fast sometimes slow. The slower it got the more of a grip it seemed to have. Ive tried new optical mice and same prob. I tried the microsoft optical mouse and ie 3.0 usb. This happens on my older computer too. I know i can take enhanced precision off but thats not the solution. I like acceleration on. I just want my mouse to be as smooth as it was at first. It really hurts me in games when i cant hit the target as great as i did before. Can someone please help me here this is a really annoying problem. Plus ive tried no drivers, ive tried drivers, different ports same problem.
Thanks

ya i know thats the thing. I gave one of the mice to my friend and it worked perfectly.